Can one use an Artificial Neural Network to determine the size of an object in a photograph?
Can one use an Artificial Neural Network to determine the size of an object in a photograph?


Yes: Learning Depth from Single Monocular Images

In the end, depth is just one special form of size.

Of course, you need something partially known, e.g. another car. You don't need to know the exact size of the car, but you know which size cars in general have. If you have an image without any reference, it is impossible.